1. Field of the Invention
The present invention relates to a stop method of a vehicle electrical power system.
2. Related Art
Fuel cell vehicles equipped with a fuel cell system as the vehicle electrical power system supply air and hydrogen to the fuel cell, and drive a drive motor using the electric power thereby generated to travel. In the fuel cell system, a battery is provided as an energy source for driving various accessories required in order to start electric power generation by the fuel cell, and stores the electric power generated by the fuel cell.
Since the supply of electric power from the battery is necessary in startup of the fuel cell system in above way, for example, the remaining amount of the battery required in a subsequent startup is ensured by continuing electrical power generation by way of the fuel cell even after a stop operation of the fuel cell system so as to charge the battery.
Incidentally, after a stop operation of the fuel cell system, in addition to charge processing after the aforementioned such stop, processing to adjust the concentration of gases inside the flow channels of air and hydrogen (hereinafter referred to as “concentration adjustment processing”) is performed. As a specific example of this concentration adjustment processing, for example, there is concentration reduction processing that causes the oxygen concentration inside of the cathode flow channel of the fuel cell to decrease to make inside of the cathode flow channel a low oxygen concentration state (nitrogen rich state) (refer to Patent Document 2). If oxygen remained inside of the cathode flow channel as is, there is concern over the cathode side of the fuel cell entering a high potential state when supplying hydrogen to the anode system during the next startup, and the solid polymer electrolyte membrane of the fuel cell degrading. The concentration reduction processing is preferably performed jointly with the above-mentioned charge processing after the stop operation of the fuel cell system in order to prevent such degradation of the fuel cell during the next startup.    [Patent Document 1] Japanese Unexamined Patent Application, Publication No. 2007-165055    [Patent Document 2] Japanese Unexamined Patent Application, Publication No. 2003-115317